We denote the set of of \(n \times n\)  DD matrices as \(DD_n\)  and the set of \(n \times n\)  SDD matrices as \(SDD_n\) . It is known that the following inclusion holds (e.g., by Gershgorin's circle theorem) [1]}
\(DD_n \subseteq SDD_n \subseteq \mathbb {S}^n_+.\) 
